Unable to eject portable drives

Try booting into Safe Mode to see how it works. If Safe Mode works, then it means you most likely have some third party software installed which is interfering with the normal operation of macOS.

If Safe Mode does not work, then you can try seeing what apps & processes are accessing the external volume by using the following command (replace "<path-to-external-volume>" with the correct path to the USB stick). You can just use the Finder to drag & drop the volume onto the open Terminal window after typing "sudo lsof " making sure to leave at least one space after "lsof ".

sudo  lsof  "<path-to-external-volume>"

FYI, the only Mac Mini you could possibly make a bootable macOS USB installer using an M2 system would be for a 2014 Mini assuming you already have a copy of Big Sur or Monterey installers archived somewhere. An Apple Silicon M-series Mac is only able to create macOS 11.x+ USB installers by using the "createinstallmedia" utility (personal experience).

Since your M2 Mini shipped with macOS 13.x Ventura, you won't be able to download the older installers since they are not compatible with your M2 Mini. I'm not entirely certain if the "createinstallmedia" command will perform any checks even if you already have a copy of the older installers already downloaded using an older Mac.

"mds" & "mds_store" are part of Spotlight. Spotlight is always a pain. You can disable spotlight indexing on the external drive by using the instructions in this Apple article:

Prevent Spotlight searches in files on Mac - Apple Support

If you want Spotlight to index that drive, then leave the drive connected until Spotlight finishes indexing it. If Spotlight should have been long done with indexing, then maybe their is a problem with the Spotlight index on that particular drive.

markfromroermond wrote:

I get the older installers via the Mist app and do use the createinstallmedia command via terminal.

You will only be able to use that utility for creating macOS 11.x+ USB installers assuming that macOS & the "creatinstallmedia" utility allows a 2023 Mac to create an installer older than macOS 13.x Ventura.

I had a 2020 M1 Mac which shipped with macOS 11.x Big Sur and was unable to create a USB installer for macOS 10.15 Catalina even though I did have an archived copy of the installer.

Maybe that USB thumb (?) drive is just too slow. I have such drive and in some recent macOS it could be formatted only as MacOS Extended because it timed out before the APFS formatting phase could be done. Later macOS fixed that but I use that old slow thumb drive only id there are no other options.

Might this explain the issue: 3rd party virus apps (Avast, AVG, Bitdefender, Intego, MacAfee, Norton, ESET NOD32, Trusteer etc) and 3rd party "cleaning", "optimizing", "speed-up" apps (CleanMyMac, MacKeeper etc) produce obscure errors.